The present invention relates to an oil leak prevention structure of vacuum pumps that draw gas by operating a gas conveying body in a pump chamber through rotation of a rotary shaft.
In a typical vacuum pump, lubricant oil is used for lubricating moving parts. Japanese Laid-Open Patent Publications No. 63-129829 and No. 3-11193 disclose vacuum pumps having structures for preventing oil from entering zones where presence of lubricant oil is undesirable.
In the vacuum pump disclosed in Publication No. 63-129829, a plate for preventing oil from entering a generator chamber is attached to a rotary shaft. Specifically, when moving along the surface of the rotary shaft toward the generator chamber, oil reaches the plate. The centrifugal force generated by rotation of the plate spatters the oil to an annular groove formed about the plate. The oil flows to the lower portion of the annular groove and is then drained to the outside along a drain passage connected to the lower portion.
The vacuum pump disclosed in Publication No. 3-11193 has an annular chamber for supplying oil to a bearing and a slinger provided in the annular chamber. When moving along the surface of a rotary shaft from the annular chamber to a vortex flow pump, oil is thrown away by the slinger. The thrown oil is then sent to a motor chamber through a drain hole connected to the annular chamber.
The plate (slinger), which rotates integrally with the rotary shaft, is a mechanism that prevents oil from entering undesirable zones. When centrifugal force generated by rotation of a plate (slinger) is used for preventing oil from entering a certain zone, the effectiveness is influenced by the shapes of the plate (slinger) and the walls surrounding the plate (slinger).
Accordingly, it is an objective of the present invention to provide an oil leak prevention mechanism that effectively prevents oil from entering a pump chamber of a vacuum pump
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, the invention provides a vacuum pump. The vacuum pump draws gas by operating a gas conveying body in a pump chamber through rotation of a rotary shaft. The vacuum pump has an oil housing member. The oil housing member defines an oil zone adjacent to the pump chamber. The rotary shaft has a projecting portion that projects from the pump chamber into the oil zone through the oil housing member. Stoppers are located on the rotary shaft to integrally rotate with the rotary shaft and prevent oil from entering the pump chamber. The stoppers are located along the axial direction of the rotary shaft.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.